This Aluminum spacer can be widely used in high-temperature, high-pressure, and highly corrosive pressure, valves, sealing parts of cylinder heads, and industries such as car, steel mills, chemical equipment, and engineering machinery.Specification Material: AluminumColor: SilverInside Diameter: 5/16" , 8.2mmLength: 4mmOutside Diameter: 16 mmCompatible Screw Size: 5/16" , M8 Screws BoltsSize: 8.2 x 16 x 4 mm / 0.323 x 0.63 x 0.157 inch (ID*OD*L)Packing List: 5 x Round Spacer AluminumAdvantageMade of durable Aluminum material, which is hard, good performance, good electrical conductivity, corrosion resistance and can be used for a long time.Instruction Easy to use, just need to install on the screw bolts with proper diameter.NOTE: Please select the appropriate size according to your needs.